tl;dr: Tarsney slightly misrepresents an existential risk estimate.
Tarsney writes:
To my knowledge, the most pessimistic estimate of near-term existential risk in the academic literature belongs to Rees (2003), who gives a 0.5 probability that humanity will not survive the next century.
But what Rees actually writes is:
I think the odds are no better than fifty-fifty that our present civilisation on Earth will survive to the end of the present century.
(Hereās one online source quoting Rees. Iāve seen the same quote elsewhere too.)
Whether āour present civilisation on Earthā survives is very different from whether humanity survives. I havenāt read Reesā book, so I donāt know what he intended that quote to mean, but Iād guess heād include things like a major population collapse that lasts a few decades as āour present civilisation on Earth not survivingā. Arguably, his forecast could even be seen as capturing the chance that we just very substantially change our political, cultural, and economic systems, in the same way as how Europe in the 1900s was arguably a ādifferent civilisationā to Europe in the year 100CE.
Also, Rees doesnāt give a 0.5 probability; he gives a probability no better than 0.5.
For a collection of such estimates, see Tonn and Stiefel (2014, pp. 134ā5).
I think itād be better to direct people to the appendix of Beard et al. (2020), since thatās more comprehensive and up-to-date. (I also really like the article itself.)
Perhaps unsurprisingly, I also think itād be even better-er to direct people to my database, since thatās even more comprehensive and up-to-date (and people can and do make suggestions to it, which I process, such that it should presumably remain the most comprehensive resource, rather than being frozen in time). But I can understand Tarsney preferring to refer readers to an academic source.
(Incidentally, if thereās anyone whoād in theory like to cite my database, but canāt do so unless itās hosted somewhere elseāe.g., a preprint serverāor needs it to look different, please let me know and Iāll see what I can do.)
Tipler doesnāt give a quantitative estimate, so maybe that shouldnāt count.
Leslie and Bostromās estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since itās possible that their overall distribution would be more pessimistic, and because Reesā estimate is not necessarily about existential catastrophe (since it could include other ways in which āour present civilisationā doesnāt āsurviveā)
Leslie and Bostromās estimates arenāt as near-term as Reesā estimate
So Tarsneyās claim is reasonable on this front; Iām just adding some extra info.
There are also some more pessimistic estimates in sources that arenāt academic but do seem similarly worth paying attention to to Reesā estimate; see my database.
tl;dr: Tarsney slightly misrepresents an existential risk estimate.
Tarsney writes:
But what Rees actually writes is:
(Hereās one online source quoting Rees. Iāve seen the same quote elsewhere too.)
Whether āour present civilisation on Earthā survives is very different from whether humanity survives. I havenāt read Reesā book, so I donāt know what he intended that quote to mean, but Iād guess heād include things like a major population collapse that lasts a few decades as āour present civilisation on Earth not survivingā. Arguably, his forecast could even be seen as capturing the chance that we just very substantially change our political, cultural, and economic systems, in the same way as how Europe in the 1900s was arguably a ādifferent civilisationā to Europe in the year 100CE.
Also, Rees doesnāt give a 0.5 probability; he gives a probability no better than 0.5.
Also, Tarsney writes:
I think itād be better to direct people to the appendix of Beard et al. (2020), since thatās more comprehensive and up-to-date. (I also really like the article itself.)
Perhaps unsurprisingly, I also think itād be even better-er to direct people to my database, since thatās even more comprehensive and up-to-date (and people can and do make suggestions to it, which I process, such that it should presumably remain the most comprehensive resource, rather than being frozen in time). But I can understand Tarsney preferring to refer readers to an academic source.
(Incidentally, if thereās anyone whoād in theory like to cite my database, but canāt do so unless itās hosted somewhere elseāe.g., a preprint serverāor needs it to look different, please let me know and Iāll see what I can do.)
tl;dr Iām aware of 1-3 other things that might count as more pessimistic estimates of near-term existential risk in the academic literature.
Specifically:
Frank Tipler wrote āPersonally, I now think we humans will be wiped out this centuryā
John Leslie estimated the risk of extinction over the next five centuries as at or above 30%.
Nick Bostrom estimates the odds that āexistential disaster will do us inā at some point as probably at or above 25%.
For further details and sources, see my Database of existential risk estimates (or similar) (see here for the accompanying post).
But:
Tipler doesnāt give a quantitative estimate, so maybe that shouldnāt count.
Leslie and Bostromās estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since itās possible that their overall distribution would be more pessimistic, and because Reesā estimate is not necessarily about existential catastrophe (since it could include other ways in which āour present civilisationā doesnāt āsurviveā)
Leslie and Bostromās estimates arenāt as near-term as Reesā estimate
So Tarsneyās claim is reasonable on this front; Iām just adding some extra info.
There are also some more pessimistic estimates in sources that arenāt academic but do seem similarly worth paying attention to to Reesā estimate; see my database.